Draw die prestretch fixture employing preloaded bearings



May 10, 1966 s. M. DOLNEY 3,250,107

DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Filed Oct. 30, 1964 6 Sheets-Sheet 1 Wm H 7 HM] 7 H 'm 9 TL J; I L F J-r- I i l F i i i I L/ l l l I i I l I L L L J--L L L i -1 I .nlh 5 I II II M ||H Ml I H WI" Lip 30 i J F Jr b A! .w MN I I /3 Z ATTORNEY.

S. M. DOLNEY May 10, 1966 DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Filed OCT 50, 1964 6 Sheets-Sheet 2 f" Arra/P/v'r May 10, 1966 s. M. DOLNEY DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Filed Oct. 30, 1964 6 Sheets-Sheet 3 i HTTORNEX May 10, 1966 s. M. DOLNEY 3,250,107

DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Filed 0011. 30, 1964 6 Sheets-Sheet 4.

INVENTOR.

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y 0, 1966 s. M. DOLNEY 3,250,107

DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Filed Oct. 30, 1964 6 Sheets-Sheet 5 INVENTOR.

BY A

ATTORNEY.

S. M. DOLNEY May 10, 1966 DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS 6 Sheets-Sheet 6 Filed Oct. 50, 1964 HI W .1"!

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United States Patent 3,250,107 DRAW DIE PRESTRETCH FIXTURE EMPLOYING PRELOADED BEARINGS Stanley M. Dolney, Parma, Ohio, assignor to The Cyril Bath Company, Solon, Ohio, a corporation of Ohio Filed Oct. 30, 1964, Ser. No. 407,780 8 Claims. (Cl. 72297) This invention relates to a draw die press and prestretch fixture combination, and particularly to an improvement disclosed in United States Letters Patent No. 3,113,607, issued December 10, 1963, Paul F. Maize, inventor.

The improvement is one wherein the horizontal movement of the stretch head toward and away from the path of the dies and the vertical movement of the stretch head are improved and frictional resistance to movement of the head, resulting from stresses imposed on the head by turning moments created by the tension on the sheet being formed, are so reduced that binding and locking of the head against vertical or horizontal movement are eliminated.

The above patent discloses a structure in which each stretch unit comprises a rigid base, and an elevator mounted in suitable vertical guideways on the base for vertical movement, and a stretch gripping head mounted on the elevator for horizontal movement toward and away from the path of the dies.

The present invention insofar 'as concerns mounting of a stretch head on its elevator is an improvement on the Maize patent, and insofar as concerns the mounting of the elevator for vertical movement, it is an improvement on the Maize patent and United States Letters Patent No. 3,116,780, issued January 7, 1964, Cyril J. Bath, inventor.

The invention may at first appear to be the mere substitution of antifriction bearing means for slide bearings with the expected result of freer movement of the stretch head, and. thus a mere matter of degree over prior mountings. In many types of machines employing a reciprocable stock working tool head, this would be true, as the head could be moved in any event by conventional power feed means, if of adequate size. The advantage of antifriction roller bearings, in such a case, would be that a smaller power feed could be used. This is because the stock does not operate the tool.

In stretch forming, however, the stock becomes an operating part of the machine temporarily, being operative to move the stretch heads against the yieldable tension applied by the hydraulic piston and cylinder assemblages holding the stock above its elastic limit. Obviously the stock size and metal are dictated by the part to be formed and cannot be adjusted for-conforming to the capabilities of the machine. To the contrary, the machine must be adjusted to conform to the limitations of the stock.

When stock is being formed under tension, sudden increases in the normal tension followed by instantaneous restoration of the normal tension cause changes in the elastic limit and ultimate strength of the sheet. Thus a jerk on a sheet of stock partway through its cycle of formation makes accurate control extremely complicated.

The piston and cylinder assemblages for applying yieldable tension cannot be adjusted promptly enough to prevent such changes if extraneously imposed.

Likewise, should the stretch head bind and lock while being drawn toward the dies by the sheet and the dies should continue to close, the tension on the sheet would rise instantly far above the elastic limit of the metal and,

depending on the length 'of the drawn stock remaining,

the tension applied to it by the sheet. Such would destroy the sheet. The increase in tension thus applied would cause even tighter binding of the head, since the increased tensi-oning force would be exactly in the direction that originally caused the binding. tension applied by the tensioning piston and cylinder assemblages would not release the locking, as the sheet would continue holding the head in binding position, and to increase the tension applied by the assemblages might pull the head out of locking relation but only by further increasing the tension on the sheet.

Since the sheet itself becomes the weakness in the machine, frustrating attempts to overcome the binding stresses by increases in applied power, the sheet cannot be accommodated to the needs of the machine. The overcoming of binding stresses, once they develop, is not possible. The only solution is to prevent their inception. Such is accomplished by the antifriction mountings herein disclosed. As a result of such mountings, the maximum capacity of the machine is limited only by the strength of its parts and its power supply.

The principal object of the present invention is to assure movement of the stretch head toward and away from the path of the dies under all operating conditions and freefrom frictional stresses which can initiate binding and lock-up of the head and elevator.

Incidental additional advantages will become apparent from the following description, wherein reference is made to the drawings, in which FIGURE 1 is a front elevation of a draw die press with the stretch units of the present invention mounted thereon;

FIG. 2 is a top plan view of one of the stretch units,

,partof the gripper and carriage being broken away for clearness in illustration;

FIG. 3 is a left side elevation of the stretch unit illustrated in FIG. 2, showing the forward face of the stretch unit exposed toward the die space of the press;

FIG. 4 is a vertical sectional view of the unit illustrated in FIG. 2, and is taken on the line 4-4 in FIG. 2;

FIG. 5 is a fragmentary vertical sectional view taken on the line 55 in FIGS. 2 and 3;

FIG. 6 is a top plan view of a modified stretch unit embodying the principles of the present invention;

FIG. 7 is a front elevation of the unit illustrated in FIG. 6, part thereof being shown in section, and

FIG. 8 is a vertical sectional view taken on line 8--8 in FIG. 7.

Referring to the drawings, the invention is shown as embodied in a conventional hydraulic press, indicated generally at 1, comprising a bed 2, and upright guide posts 3 arranged at the corners and guiding a ram or platen 4 for vertical reciprocation. The bed supports a male die 5 and the ram supports a complementary female die 6, the dies 5 and 6 being conventional drawing dies.

The ram is driven on its forming and return strokes by means of hydraulic piston and cylinder assemblages 7, comprising cylinders 8 and pistons 9 reciprocable therein and having piston rods 10 secured to the ram 4. Mounted on the bed 2 is a prestretch, apparatus, which, in the form illustrated, comprises two units 11 arranged on the bed, one unit at each end of the male die 5. The units 11 are the same in form and function and only one unit will be described in detail. p

Referring particularly to FIGURES 2 through 5, each unit somprises a base plate 13 on the ends of which are mounted guide supports 14 which support upright guides 15. Each guide 15 has upright slide surfaces 16 which,

- in a direction forwardly and rearwardly of the press bed,

face inwardly. The guides have upright faces 17 which are at right angles to the surfaces 16 and face in a direction toward and away from the dies, which is the tensioning direction.

To reduce or release the Mounted for vertical reciprocation in the upright guides 15, as will later be described, is a stretch head elevator 20 which is guided for movement upwardly and downwardly while the elevator itself remains parallel to its starting position. v

For moving the elevator 20 upwardly and downwardly, suitable piston and cylinder assemblages 21 are provided, one at each end of the elevator. Each assemblage comprises a cylinder 22 mounted in fixed position on the support 14, piston 23 which is reciprocable in the cylinder and having a piston rod 24. The cylinder 22 is arranged so that the piston rod 24 extends upwardly and at its upper end is connected to a plate 25 which, in turn, is connected to the elevator 20. Thus, upon introduction of hydraulic pressure fluid to the rod ends of the cylinders 22, the pistons move the elevator downwardly, and by introduction of fluid to the head ends of the cylinders 22, the pistons move the elevator 20 upwardly.

In order to stretch the stock into and above its elastic limits independently of the dies, suitable grippers 30 are provided, one for each unit 11. Each gripper comprises an elongated body or stretch head 31 which extends for- .wardly endwise and rearwardly of the press bedand, thus transversely of the direction in which the stock is to be tensioned. Each head has complementary gripping jaws 32 and 32a which are cooperable with cam surfaces 33 and 33a for gripping the stock. Each pair of jaws extends substantially the full length of the head 31. To close and open the jaws, each gripper 30 is provided with a plurality of cylinders 36, in which pistons 37, having rods 38 connected to the jaws, are reciprocable, respectively. The cylinders are connected in parallel at their rod ends to a manifold 42 and connected in parallel at their head ends to a manifold 43 so that all operate concurrently.

As mentioned hereinbefore, it is desirable that each stretch head be arranged so that it can move toward and away from the dies under yieldable resistance of the stretch forming pressure without binding and with a negligible amount of frictional stresses. For this purpose, the gripper 30 is mounted on a carriage or support 45 which, in turn, is :mounted on the elevator 20 for horizontal movement relative thereto toward and away from the adjacent ends of the dies. Each carriage supports, in depending relation therefrom and in rigidly fixed position relative thereto an underplate 46 which, in turn, supports a cylinder block 47. The cylinder block has a plurality of bores forming cylinders 48 therein. Pistons 49, having rods 50, are reciprocable in the cylinders 48. The rods of the piston are connected by suitable bolts 51 to the forward wall of the elevator 20, which faces the dies. Pressure fluid is supplied at the rod ends of the cylinders through a line 52 and manifold duct 53, and to the head ends of the cylinder by a line 54 and manifold duct 55, so that all of the cylinders are in parallel. Thus, when pressure fluid is admitted to the rod end of the cylinder the carriage 45 is moved toward the dies, and when pressure fluid is admitted to the head ends of the cylinders the carriage 45 is moved away from the dies. It is apparent that when tension is applied to the stock by moving the carriage 45, and thereby the gripper 30 away from the dies, a turning moment is imposed by the gripper 30 on the carriage 45, tending to cause the carriage to rock about a horizontal axis extending forwardly and rearwardly of the press bed. These turning moments, due to the heavy tonnages employed for stretching, tend to cause the carriage to bind on the elevator and become self-locking against movement toward the dies, thus imposing undue tension on the stock being drawn in by the dies.

To eliminate this condition, the elevator is provided with a rigid top plate 60 which extends forwardly and rearwardly of the press beyond the ends of the grippers 30. The plate 60 has a number of passages 61 extending therethrough from top to bottom and elongated in a direction toward and away from the dies. For connecting the carriages 45 to the plate 6% and thus to the elevator 2t), suitable spacing blocks 62 extend through the passages 61 and are seated at the top in suitable channels in the underface of the carriage 45 and at the bottom in suitable channels in the upper face of the underplate 46. The plates 46, block 62 and carriage 45 are drawn tightly into seating position by bolts 65.

At spaced intervals along the carriage 45, in a direction forwardly and rearwardly of the press, the top plate 66 of the elevator is provided with channels in which are secured hardened wear strips 66 and 66, these strips extending in a direction of movement of the stretch head carriage relative to the elevator and toward and away from the dies. Mounted in suitable sockets 67, on the underside of the carriage 45 are rows of roller bearing sets 68 of the recirculating type, such as disclosed in United States Patent No. 3,003,828, issued October 10, 1961, James A. Stark, and entitled Recirculating Bearing.

In the form illustrated, the rows extend forwardly and reanwardly of the press bed and two rows of sets are provided. One row is near the die side of the elevator 20 and one near the opposite side. Each row includes a plurality of bearing units 68 spaced apart from each other in a direction endwise of the carriages 45. Similarly, the plate 46 is provided with suitable sockets 69, in which are correspondingly mounted recirculating antifricion roller bearing sets 70, the latter sets beingarranged so that one set 70 is opposite a corresponding set 68. The sets are positioned to ride on aligned ones of the upper and lower hardened strips 66 and 66. The sets are so arranged in their sockets, by shims or otherwise, so that when the carriage 45 and plate 46 are drawn firmly into clam-ping position against the opposite faces of the spacing blocks 62, the rollers of the bearings are preloaded.

It has been found that with preloaded bearings arranged in this manner, frictional stresses which would otherwise occur and bind or lock the carriage 45 against movement relative to the elevators toward and away from the dies are eliminated under all operating conditions of the stretch units. Further, it has been found that without the roller bearings, the carriage cannot be used effectively for its intended purpose if heavy tensioning forces are necessary due to the size and thickness of the sheet and materal. This is because of the turning moment imposed on the carriage 45 by the tension on the stock acting through the gripper 30. Once this turn-ing moment has established any binding of the carriage on the elevator, any increase in tension merely increases the binding action and locks the carriage, and thereby the head, against further travel toward the dies. Consequently, if continned movement of the dies toward closed position demands further movement of the grippers 30 toward the dies, the sheet is overstressed, changing the quality of the finished article, or is fractured. Consequently, for heavy duty work, the roller bearings become essential if the head is to move forwardly and rearwardly on the guides of the general character described during die drawing.

Tensioning forces on the carriage 45 also impose on the elevator turning moments tending to rotate the elevator about a horizontal axis extending forwardly and rearwardly of the press bed. In order to resist these moments so as to prevent locking up of the elevator, the guides 15 on the elevator supports at 14, the faces 17 thereof, which face in the tensioning direction, are provided with suitable sockets 71 opening toward the elevator. Set 72 of recirculating antifraction roller bearings are mounted in the sockets 71, respectively. The sets 72 are in vertical rows, respectively, and roll against suitable hardened wear strips 73 on the elevator. The sets 72 are also slightly preloaded by shims or otherwise during the mounting of the elevator between the guides 15. Thus, throughout all operations, the antifriction mountings for the carriages and elevators prevent the initiation of any bind-ing due to turning momen-ts imposed by the tension on the stock, and by eliminating the initiation thereof, assure that the tension applied by the cylinder is fully transferred to the stock and the stock is subject only to tension dictated by the hydraulic pressure in the cylinders. This assures accuracy in control.

The manner of operating the stretch heads and the like are disclosed in detail in the above identified patent, but for convenience in illustration, they are shown herein diagrammatically. For lowering and raising the press, pressure fluid is supplied to the ram assemblages 7 from a pump 78, driven by a motor 79. The'iiuid is supplied through a remotely con-trolled stop and reversing valve- 80, as indicated in FIGURE 1.

The stretch forming pressure fluid is supplied to the lines 52 and 54 of the unit by a suitable pump 82 driven by electric motor 83. The flow of dluid is controlled by a solenoid operated reversing valve 84.

Pressure fluid for closing the jaws is supplied from either pump, preferably the pump 82, through line 85 and a reversing valve 86. The specific manner of operating these various parts form no part of the present invenfor movement in a-path toward and away from the bed,

eliminated and the carriage is free to move horizontally and the elevator vertically.

Thus, in the present combinations the rollers become essential for operativeness in heavy duty combined stretch and die drawing of sheet metal because of the sheet metal functioning to drive part of the machine, whereas in other metal working machine heads, the rollers would merely relieve frictional resistance in the machine, to an extent permitting less powerful feed mechanisms, as the heads are not driven by the stock.

Having thus described my invention, I claim:

, 1. In a drawing die press and prestretch unit combination, a frame member, a bed, a ram mounted on the frame a movable elevator member movable in an upright path, a movable carriage member movable in a horizontal path toward and away from the ram path, one of said movable members being supported by the other movable member for movement relative to the other movable member for movement relative to the frame along the path of tion, which is concerned only with the mounting of the elevators in their guides and the mounting of the carriages on the elevators.

Referring next to FIGURES 6 and 7, a modification of the present invention is shown, wherein the antifriction mounting is for the type of underreach structure such as disclosed in my copending application entitled Combined Drawing Die Press and Stretch Forming Apparatus.

As therein shown and described in detail, the stretch forming unitcomprises a saddle 87 mounted on an extension of the frame of the press for adjustment toward and away from the dies of the press. Instead of mounting the elevator for vertical movement on the frame, a carriage 88 for the grippers is mounted on the saddle for lineal guided movement in upper and lower sets of preloaded antifriction bearings 89 and 90. The sets are supported in position in the saddle 87. The advantage of this arrangement, as pointed out in the above application, is that a much longer carriage can be accommodated readily on the frame than on the elevator of the structure heretofore described. Thus the sets of bearings 89 and 90, cor-responding to the sets 67 and 69 heretofore described, can be spaced further apart in a direction toward and away from the dies for better withstanding turning movements and reducing the unit force imposed by the carriage on its support. On the other hand, an elevator 91 is mounted on guideways 92 on a pedestal 93 which is rigid with, and forms part of,

the carriage 88. The elevator carries a gripper 94. The

elevator 91 also carries recirculating antifriotion roller sets 95 which roll on the guideways 92. However, these sets do not have to be spaced so far apart from each other as the sets 89 or 90, because the turning moment imposed on the elevator 93 and tending to bind it on the guideways are small in proportion to those imposed on the carriage. This is because the tension on the stock during initial stretching is in a plane intersecting the guides 92 at 90 thereto; that is, in a horizontal plane between the upper and lower sets of bearings. Hence the stress on the bearings 95 is a direct compression stress. 7

As illustrated, tensioning force is provided by reversible piston and cylinder assemblages 96, including cylinders 97 connected to the saddle 87, and with pistons 98 having piston rods 99 connected at their outer ends to the carriage The elevator is raised and lowered by reversible piston and cylinder assemblages 98, arranged one at each end of the unit and supported on the pedestal 93. Thus, in all cases, initial binding due to tensioning of the stock is said other movable member, power means respective to the ram, the one movable member and the other movable member, for moving them along their paths, respectively, sets of recirculating roller bearings interposed between at least one of the movable members and the member by which it supported and antifrictionally supporting the last mentioned supported movable member on the member supporting it, means preloading said recirculating roller bearings, and a stock gripper carried by one of the movable members for concurrent movement by the movable members in both of said paths of the movable members.

2. An apparatus according to claim 1 wherein sets of recirculating roller bearing means are interposed between each movable member and the member by which it is supported for antifrictionally supporting each movable member on the member supporting it, and all of said roller bearings are preloaded.

3. In a drawing die press and prestretch unit combination, a frame, a ram supported thereby for movement along an upright path, ram power means for driving the ram, an elevator mounted on the frame for movement along a predetermined upright path to raised and lowered positions, elevator power means for moving the elevator to said positions, selectively, a gripper carriage, horizontal guideways on the elevator and carriage, respectively, extending toward .and away from the ram path, and arranged in sets, recirculating roller bearings for supporting the carriage on the elevator for movement relative thereto in opposite directions along the guideways, carriage power means for moving the carriage along the guideways, said roller bearings being secured in fixed position endwise of the guideways on one of the guideways of each set of guideways with its rollers in rolling engagement with the other guideway of the same set of guideways, means mounting the roller bearings in preloaded condition between and relative to the guideways, and a gripper connected to the carriage for movement therewith.

4. An apparatus according to claim 3 wherein, of the sets of guideways of the elevator and carriage, one guideway of each set has an upper downwardly facing guide surface and a lower upwardly facing guide surface, and the other guideway of the same set has an upper upwardly facing guide surface complementary to said upper downwardly facing guide surface and forming therewith one pair of complementary guide surfaces and a lower downwardly facing guide surface complementary to said lower upwardly facing guide surface and forming therewith another pair of complementary guide surfaces, and a plurality of said rollers are interposed between the complementary surfaces of each pair of surfaces of each set of guideways. 1

5. An apparatus according to claim 3 wherein the frame has upright elevator guideways, the elevator has upright elevator guideways complementary to those on the frame, respectively, and recirculating antifiriction rollers are interposed in preloaded condition between the complementary pairs of elevator guideways for antifrictionally supporting the elevator for movement in its upright path.

6. In a drawing die press and prestretch unit combination, a frame, a bed, a ram mounted on the frame for movement in a path toward and away from the bed, a gripper carriage, horizontal cooperable guideways on the frame and carriage, respectively, extending toward and away from the ram path and arranged in sets, for supporting and guiding the carriage for movement in opposite directions along the guideways, carriage power means for moving the carriage along said guideways, an elevator mounted on the carriage for movement along an upright path relative thereto, elevator power means for moving the elevator, sets of recirculating roller bearings secured in fixed position endwise of the guideways on one of the guideways of each set of guideways with the rollers in rolling engagement with the other guide- Way of the same set of guideways, means mounting the roller bearings in preloaded condition between, and relative to the guideways, and a gripper connected to the elevator for movement therewith.

7. The structure according to claim 6 wherein of the sets of guideways of the carriage and frame, one guideway of each set has an upper downwardly facing guide surface and a lower upwardly facing guide surface, and

the other guideway 0f the same set has an upper upwardly facing guide surface complementary to said upper downwardly facing guide surface and forming therewith one pair of complementary guide surfaces and a lower downwardly facing guide surface complementary to said lower upwardly facing guide surface and forming therewith another pair of complementary guide surfaces, and said set of rollers areinterposed between each complementary pair of surfaces of each set of guideways.

8. An apparatus according to claim 6 wherein the frame has upright elevator guideways, the elevator has upright elevator guideways complementary to those on the frame, respectively, and recirculating antifriction rollers are interposed in preloaded condition between the complementary pairs of elevator guideways for antifrictionally supporting the elevator for movement in its upright path.

References Cited by the Examiner UNITED STATES PATENTS 2,446,089 7/1948 Hochreiter 72-297 3,003,828 10/1961 Stark 3086 3,113,607 12/1963 Maize. 3,116,780 1/1964 Bath.

FOREIGN PATENTS 964,310 7/ 1964 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Examiner. 

1. IN A DRAWING DIE PRESS AND PRESTRETCH UNIT COMBINATION, A FRAME MEMBER, A BED, A RAM MOUNTED ON THE FRAME FOR MOVEMENT IN A PATH TOWARD AND AWAY FROM THE BED, A MOVABLE ELEVATOR MEMBER MOVABLE IN AN UPRIGHT PATH, A MOVABLE CARRIAGE MEMBER MOVABLE IN A HORIZONTAL PATH TOWARD AND AWAY FROM THE RAM PATH, ONE OF SAID MOVABLE MEMBERS BEING SUPPORTED BY THE OTHER MOVABLE MEMBER FOR MOVEMENT RELATIVE TO THE OTHER MOVABLE MEMBER ALONG THE PATH OF SAID ONE MOVABLE MEMBER, THE OTHER MOVABLE MEMBER BEING SUPPORTED BY THE FRAME MEMBER FOR MOVEMENT RELATIVE TO THE FRAME ALONG THE PATH OF SAID OTHER MOVABLE MEMBER, POWER MEANS RESPECTIVE TO THE RAM, THE ONE MOVABLE MEMBER AND THE OTHER MOVABLE MEMBER, FOR MOVING THEM ALONG THEIR PATHS, RESPECTIVELY SETS OF RECIRCULATING ROLLER BEARINGS INTERPOSED BETWEEN AT 